Enhanced transmission time interval bundling design for machine type communications

ABSTRACT

Aspects of the present disclosure provide techniques for enhanced transmission time interval (TTI) bundling design for machine type communications (MTC). A method for wireless communications by a wireless device is provided. The method generally includes determining a mapping of one or more uplink or downlink channels to one or more fixed bundling sizes, wherein each of the one or more fixed bundling sizes indicates a number of transmission time intervals (TTIs) over which a channel should be transmitted and processing transmission of the one or more uplink or downlink channels based on the mapping.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 61/809,184, filed Apr. 5, 2013, which is herein incorporated byreference in its entirety.

BACKGROUND

I. Field

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to techniques for enhancedtransmission time interval (TTI) bundling design for machine typecommunications (MTC).

II. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE)/LTE-Advanced systems andorthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-input single-output, multiple-inputsingle-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of base stationsthat can support communication for a number of wireless devices.Wireless devices comprise user equipments (UEs) and remote devices. A UEmay be a device that operates under direct control by humans. Someexamples of UEs include cellular phones, smart phones, personal digitalassistants (PDAs), wireless modems, handheld devices, laptop computers,tablets, netbooks, smartbooks, ultrabooks, etc. A remote device may be adevice that operates without being directly controlled by humans. Someexamples of remote devices include sensors, meters, monitors, locationtags, etc. A remote device may communicate with a base station, anotherremote device, or some other entity. Machine type communication (MTC)refers to communication involving at least one remote device on at leastone end of the communication.

SUMMARY

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to techniques for enhancedtransmission time interval (TTI) bundling design for machine typecommunications (MTC).

Certain aspects of the present disclosure provide a method,corresponding apparatuses and program products, for wirelesscommunications by a wireless device. The method generally includesdetermining a mapping of one or more uplink or downlink channels to oneor more fixed bundling sizes, wherein each of the one or more fixedbundling sizes indicates a number of transmission time intervals (TTIs)over which a channel should be transmitted and processing transmissionof the one or more uplink or downlink channels based on the mapping.

In aspects, the corresponding apparatus generally includes means fordetermining a mapping of one or more uplink or downlink channels to oneor more fixed bundling sizes, wherein each of the one or more fixedbundling sizes indicates a number of transmission time intervals (TTIs)over which a channel should be transmitted and means for processingtransmission of the one or more uplink or downlink channels based on themapping.

In aspects, the corresponding apparatus generally includes at least oneprocessor configured to determine a mapping of one or more uplink ordownlink channels to one or more fixed bundling sizes, wherein each ofthe one or more fixed bundling sizes indicates a number of transmissiontime intervals (TTIs) over which a channel should be transmitted andprocess transmission of the one or more uplink or downlink channelsbased on the mapping. The apparatus generally also includes a memorycoupled with the at least one processor.

In aspects, the corresponding computer program generally includes acomputer readable medium having instructions stored thereon, theinstructions executable by one or more processors, for determining amapping of one or more uplink or downlink channels to one or more fixedbundling sizes, wherein each of the one or more fixed bundling sizesindicates a number of transmission time intervals (TTIs) over which achannel should be transmitted; and processing transmission of the one ormore uplink or downlink channels based on the mapping.

Certain aspects of the present disclosure provide a method,corresponding apparatuses and program products, for wirelesscommunications by a wireless device. The method generally includesdetermining persistent scheduling (PS) assignment for a bundling sizespecifying a number of transmission time intervals (TTIs) to be used fortransmissions of at least one channel, transmitting the at least onechannel in one or more TTIs, and terminating transmission of the atleast one channel prior to reaching the number of TTIs specified by thebundling size, in response to receiving an indication a receiving devicesuccessfully received the at least one channel.

Certain aspects of the present disclosure provide a method,corresponding apparatuses and program products, for wirelesscommunications by a wireless device. The method generally includesreceiving an indication of persistent scheduling (PS) assignment for abundling size specifying a number of transmission time intervals (TTIs)to be used for transmissions of at least one channel, receiving the atleast one channel in one or more TTIs, and transmitting an indication toterminate transmission of the at least one channel prior to reaching thenumber of TTIs specified by the bundling size, if the at least onechannel is received successfully.

Certain aspects of the present disclosure provide a method,corresponding apparatuses and program products, for wirelesscommunications by a wireless device. The method generally includesdetermining persistent scheduling (PS) assignment for a fixed number ofresource blocks (RBs) to transmit at least one channel and adjusting atleast one a modulation and coding scheme (MCS), rate, or transmit powerwhen transmitting the at least one channel.

Certain aspects of the present disclosure provide a method,corresponding apparatuses and program products, for wirelesscommunications by a wireless device. The method generally includesdetermining persistent scheduling (PS) assignment for a fixed number ofresource blocks (RBs) to transmit at least one channel and processing atransmission of the at least one channel, wherein at least one of amodulation and coding scheme (MCS), rate, or transmit power may beadjusted when transmitting the at least one channel.

Numerous other aspects are provided including methods, apparatus,systems, computer program products, and processing systems.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an example of awireless communication network, in accordance with certain aspects ofthe present disclosure.

FIG. 2 shows a block diagram conceptually illustrating an example of abase station in communication with a user equipment (UE) in a wirelesscommunications network, in accordance with certain aspects of thepresent disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of aframe structure in a wireless communications network, in accordance withcertain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating two exemplarysubframe formats with the normal cyclic prefix.

FIG. 5 illustrates example operations for enhanced uplink coverage thatmay be performed by a wireless device, in accordance with certainaspects of the present disclosure.

FIG. 6 illustrates example operations for enhanced uplink coverage thatmay be performed by a wireless device, in accordance with certainaspects of the present disclosure.

FIG. 7 illustrates example operations for enhanced uplink coverage thatmay be performed by a wireless device, in accordance with certainaspects of the present disclosure.

FIG. 8 illustrates example operations for enhanced uplink coverage thatmay be performed by a wireless device, in accordance with certainaspects of the present disclosure.

FIG. 9 illustrates example operations for enhanced uplink coverage thatmay be performed by a wireless device, in accordance with certainaspects of the present disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques for enhancedtransmission time interval (TTI) bundling design for machine typecommunications (MTC). TTI bundling size may be fixed by a one-to-one ora one-to-many mapping. Bundling sizes may be determined for a channelbased on bundling sizes used for signaled by another channel. Persistentscheduling can also be used to transmit a channel, where a modulationand coding scheme (MCS), rate, or transmit power can be adjusted fortransmission of the channel.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the wireless networks and radio technologies mentioned above aswell as other wireless networks and radio technologies. For clarity,certain aspects of the techniques are described below forLTE/LTE-Advanced, and LTE/LTE-Advanced terminology is used in much ofthe description below.

An Example Wireless Communications System

FIG. 1 shows a wireless communication network 100, which may be an LTEnetwork or some other wireless network. Wireless network 100 may includea number of evolved Node Bs (eNBs) 110 and other network entities. AneNB is an entity that communicates with user equipments (UEs) and mayalso be referred to as a base station, a Node B, an access point, etc.Each eNB may provide communication coverage for a particular geographicarea. In 3GPP, the term “cell” can refer to a coverage area of an eNBand/or an eNB subsystem serving this coverage area, depending on thecontext in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell,a femto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a pico cell may be referred to asa pico eNB. An eNB for a femto cell may be referred to as a femto eNB ora home eNB (HeNB). In the example shown in FIG. 1, an eNB 110 a may be amacro eNB for a macro cell 102 a, an eNB 110 b may be a pico eNB for apico cell 102 b, and an eNB 110 c may be a femto eNB for a femto cell102 c. An eNB may support one or multiple (e.g., three) cells. The terms“eNB”, “base station” and “cell” may be used interchangeably herein.

Wireless network 100 may also include relay stations. A relay station isan entity that can receive a transmission of data from an upstreamstation (e.g., an eNB or a UE) and send a transmission of the data to adownstream station (e.g., a UE or an eNB). A relay station may also be aUE that can relay transmissions for other UEs. In the example shown inFIG. 1, a relay station 110 d may communicate with macro eNB 110 a and aUE 120 d in order to facilitate communication between eNB 110 a and UE120 d. A relay station may also be referred to as a relay eNB, a relaybase station, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes eNBsof different types, e.g., macro eNBs, pico eNBs, femto eNBs, relay eNBs,etc. These different types of eNBs may have different transmit powerlevels, different coverage areas, and different impact on interferencein wireless network 100. For example, macro eNBs may have a hightransmit power level (e.g., 5 to 40 Watts) whereas pico eNBs, femtoeNBs, and relay eNBs may have lower transmit power levels (e.g., 0.1 to2 Watts).

A network controller 130 may couple to a set of eNBs and may providecoordination and control for these eNBs. Network controller 130 maycommunicate with the eNBs via a backhaul. The eNBs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wirelessnetwork 100, and each UE may be stationary or mobile. A UE may also bereferred to as an access terminal, a terminal, a mobile station, asubscriber unit, a station, etc. A UE may be a cellular phone, apersonal digital assistant (PDA), a wireless modem, a wirelesscommunication device, a handheld device, a laptop computer, a cordlessphone, a wireless local loop (WLL) station, a tablet, a smart phone, anetbook, a smartbook, an ultrabook, etc.

FIG. 2 shows a block diagram of a design of base station/eNB 110 and UE120, which may be one of the base stations/eNBs and one of the UEs inFIG. 1. Base station 110 may be equipped with T antennas 234 a through234 t, and UE 120 may be equipped with R antennas 252 a through 252 r,where in general T≧1 and R≧1.

At base station 110, a transmit processor 220 may receive data from adata source 212 for one or more UEs, select one or more modulation andcoding schemes (MCS) for each UE based on CQIs received from the UE,process (e.g., encode and modulate) the data for each UE based on theMCS(s) selected for the UE, and provide data symbols for all UEs.Transmit processor 220 may also process system information (e.g., forSRPI, etc.) and control information (e.g., CQI requests, grants, upperlayer signaling, etc.) and provide overhead symbols and control symbols.Processor 220 may also generate reference symbols for reference signals(e.g., the CRS) and synchronization signals (e.g., the PSS and SSS). Atransmit (TX) multiple-input multiple-output (MIMO) processor 230 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, the overhead symbols, and/or the reference symbols, ifapplicable, and may provide T output symbol streams to T modulators(MODs) 232 a through 232 t. Each modulator 232 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 232 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. T downlink signals from modulators 232 a through 232 tmay be transmitted via T antennas 234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom base station 110 and/or other base stations and may providereceived signals to demodulators (DEMODs) 254 a through 254 r,respectively. Each demodulator 254 may condition (e.g., filter, amplify,downconvert, and digitize) its received signal to obtain input samples.Each demodulator 254 may further process the input samples (e.g., forOFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtainreceived symbols from all R demodulators 254 a through 254 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 258 may process (e.g., demodulateand decode) the detected symbols, provide decoded data for UE 120 to adata sink 260, and provide decoded control information and systeminformation to a controller/processor 280. A channel processor maydetermine RSRP, RSSI, RSRQ, CQI, etc.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, etc.) fromcontroller/processor 280. Processor 264 may also generate referencesymbols for one or more reference signals. The symbols from transmitprocessor 264 may be precoded by a TX MIMO processor 266 if applicable,further processed by modulators 254 a through 254 r (e.g., for SC-FDM,OFDM, etc.), and transmitted to base station 110. At base station 110,the uplink signals from UE 120 and other UEs may be received by antennas234, processed by demodulators 232, detected by a MIMO detector 236 ifapplicable, and further processed by a receive processor 238 to obtaindecoded data and control information sent by UE 120. Processor 238 mayprovide the decoded data to a data sink 239 and the decoded controlinformation to controller/processor 240. Base station 110 may includecommunication unit 244 and communicate to network controller 130 viacommunication unit 244. Network controller 130 may include communicationunit 294, controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at basestation 110 and UE 120, respectively. Processor 240 and/or otherprocessors and modules at base station 110, and/or processor 280 and/orother processors and modules at UE 120, may perform or direct processesfor the techniques described herein. Memories 242 and 282 may store dataand program codes for base station 110 and UE 120, respectively. Ascheduler 246 may schedule UEs for data transmission on the downlinkand/or uplink.

When transmitting data to the UE 120, the base station 110 may beconfigured to determine a bundling size based at least in part on a dataallocation size and precode data in bundled contiguous resource blocksof the determined bundling size, wherein resource blocks in each bundlemay be precoded with a common precoding matrix. That is, referencesignals such as UE-RS and/or data in the resource blocks may be precodedusing the same precoder. The power level used for the UE-RS in each RBof the bundled RBs may also be the same.

The UE 120 may be configured to perform complementary processing todecode data transmitted from the base station 110. For example, the UE120 may be configured to determine a bundling size based on a dataallocation size of received data transmitted from a base station inbundles of contiguous resource blocks (RBs), wherein at least onereference signal in resource blocks in each bundle are precoded with acommon precoding matrix, estimate at least one precoded channel based onthe determined bundling size and one or more reference signals (RSs)transmitted from the base station, and decode the received bundles usingthe estimated precoded channel.

FIG. 3 shows an exemplary frame structure 300 for FDD in LTE. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each radio frame may thus include 20 slots withindices of 0 through 19. Each slot may include L symbol periods, e.g.,seven symbol periods for a normal cyclic prefix (as shown in FIG. 2) orsix symbol periods for an extended cyclic prefix. The 2L symbol periodsin each subframe may be assigned indices of 0 through 2L-1.

In LTE, an eNB may transmit a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) on the downlink in the center1.08 MHz of the system bandwidth for each cell supported by the eNB. ThePSS and SSS may be transmitted in symbol periods 6 and 5, respectively,in subframes 0 and 5 of each radio frame with the normal cyclic prefix,as shown in FIG. 3. The PSS and SSS may be used by UEs for cell searchand acquisition. The eNB may transmit a cell-specific reference signal(CRS) across the system bandwidth for each cell supported by the eNB.The CRS may be transmitted in certain symbol periods of each subframeand may be used by the UEs to perform channel estimation, channelquality measurement, and/or other functions. The eNB may also transmit aphysical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 ofcertain radio frames. The PBCH may carry some system information. TheeNB may transmit other system information such as system informationblocks (SIBs) on a physical downlink shared channel (PDSCH) in certainsubframes. The eNB may transmit control information/data on a physicaldownlink control channel (PDCCH) in the first B symbol periods of asubframe, where B may be configurable for each subframe. The eNB maytransmit traffic data and/or other data on the PDSCH in the remainingsymbol periods of each subframe.

FIG. 4 shows two exemplary subframe formats 410 and 420 with the normalcyclic prefix. The available time frequency resources may be partitionedinto resource blocks. Each resource block may cover 12 subcarriers inone slot and may include a number of resource elements. Each resourceelement may cover one subcarrier in one symbol period and may be used tosend one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may betransmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11. Areference signal is a signal that is known a priori by a transmitter anda receiver and may also be referred to as pilot. A CRS is a referencesignal that is specific for a cell, e.g., generated based on a cellidentity (ID). In FIG. 4, for a given resource element with label Ra, amodulation symbol may be transmitted on that resource element fromantenna a, and no modulation symbols may be transmitted on that resourceelement from other antennas. Subframe format 420 may be used with fourantennas. A CRS may be transmitted from antennas 0 and 1 in symbolperiods 0, 4, 7 and 11 and from antennas 2 and 3 in symbol periods 1 and8. For both subframe formats 410 and 420, a CRS may be transmitted onevenly spaced subcarriers, which may be determined based on cell ID.CRSs may be transmitted on the same or different subcarriers, dependingon their cell IDs. For both subframe formats 410 and 420, resourceelements not used for the CRS may be used to transmit data (e.g.,traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211,entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); PhysicalChannels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplinkfor FDD in LTE. For example, Q interlaces with indices of 0 through maybe defined, where Q may be equal to 4, 6, 8, 10, or some other value.Each interlace may include subframes that are spaced apart by Q frames.In particular, interlace q may include subframes q, q+Q, q+2Q, etc.,where qε{0, . . . , Q−1}.

The wireless network may support hybrid automatic retransmission request(HARQ) for data transmission on the downlink and uplink. For HARQ, atransmitter (e.g., an eNB) may send one or more transmissions of apacket until the packet is decoded correctly by a receiver (e.g., a UE)or some other termination condition is encountered. For synchronousHARQ, all transmissions of the packet may be sent in subframes of asingle interlace. For asynchronous HARQ, each transmission of the packetmay be sent in any subframe.

A UE may be located within the coverage of multiple eNBs. One of theseeNBs may be selected to serve the UE. The serving eNB may be selectedbased on various criteria such as received signal strength, receivedsignal quality, pathloss, etc. Received signal quality may be quantifiedby a signal-to-noise-and-interference ratio (SINR), or a referencesignal received quality (RSRQ), or some other metric. The UE may operatein a dominant interference scenario in which the UE may observe highinterference from one or more interfering eNBs.

Example Enhanced TTI Bundling Design for MTC

The focus of the traditional LTE design is on the improvement ofspectral efficiency, ubiquitous coverage, and enhanced quality ofservice (QoS) support, etc. Current LTE system DL and uplink UL linkbudgets are designed for coverage of high end devices, such asstate-of-the-art smartphones and tablets. However, low cost low ratedevices need to be supported as well. For example, for MTC, maximumbandwidth may be reduced, a single receive radio frequency (RF) chainmay be used, peak rate may be reduced, transmit power may be reduced,and half duplex operation may be performed.

In addition to low cost, link budget requirements could be increased,for example, 20 dB coverage enhancement to cover devices in thebasement. In order to meet this coverage increase, large TTI bundlinghas been proposed to achieve 20 dB link budget gain. For example,transmission time interval (TTI) bundling with large bundling size forboth downlink (e.g., physical broadcast channel (PBCH), physicaldownlink control channel (PDCCH) and enhanced PDCCH, physical hybridautomatic repeat request (HARQ) indicator channel (PHICH), and physicaldownlink shared channel (PDSCH)) and uplink (e.g., random access channel(RACH), physical uplink control channel (PUCCH), and physical uplinkshared channel (PUSCH)) channels may be used.

However, with large TTI bundling size, power consumption and systemefficiency are a concern, particularly, for a UE to support largebundling for both DL and UL. For example, the UE may be need to supportbundling of 64 to get PDCCH grant, then transmit with PUSCH bundling of128, then receive DL ACK with bundling of 16, etc.

In certain systems (e.g., long term evolution (LTE) Release 8), TTI(e.g., subframe) bundling may be configured on a per user equipment (UE)basis. The subframe bundling operation is configured by the parameterttiBundling, which is provided by higher layers. Typically, TTI bundlingis performed by sending data from a UE in an uplink shared channel overmultiple TTIs to the base station—bundling is not applied to otheruplink signals/traffic (e.g., uplink control information).

The bundling size is fixed at 4 TTIs (subframes), that is, PUSCH istransmitted in four consecutive subframes and the same HARQ processnumber is used in each of the bundled subframes. The resource allocationsize is restricted to no more than three resource blocks (RBs). Themodulation order is set to 2 (quadrature phase-shift keying (QPSK)).Each bundle is treated as a single resource, for example, a single grantand a single HARQ acknowledgment (ACK) are used for each bundle.

TTI bundling is typically used for low rate traffic. For example, ifvoice over internet protocol (VoIP) packets cannot be transmitted in asingle TTI due to a low uplink link budget, Layer 2 (L2) segmentationmay be applied. For example, a VoIP packet may be segmented in fourradio link control (RLC) protocol data units (PDUs) that are transmittedin four consecutive TTIs. 2-3 HARQ retransmissions may be targeted toachieve sufficient coverage.

However, the conventional approach may be inefficient. Each additionalsegment introduces a 1 byte RLC, 1 byte medium access control (MAC), and3 byte L1 cyclic redundancy check (CRC) overhead. This may amount to,for example, a 15% overhead assuming a 33 byte RLC service data unit(SDU) size. In the case of 4 segments, there is an additional L1/L2overhead of 45%.

Another drawback to the conventional approach is that HARQtransmissions/retransmissions for every segment may require grants onPDCCH, consuming significant PDCCH resources. Additionally, each HARQtransmission or retransmission is followed by HARQ feedback on PHICH.Assuming a NACK/ACK error ratio of 10⁻³, the large number of HARQfeedback signals leads to high packet loss probabilities. For example,if 12 HARQ feedback signals are sent, the HARQ feedback error ratio maybe on the order of 1.2*10⁻². Packet loss rates of more than 10⁻² areunacceptable for VoIP traffic.

Usage of only a single uplink grant and a single PHICH signal per TTIbundle would be advantageous. L1 and L2 overhead may be minimized sinceno L2 segmentation is required. Coverage improvements for medium datarate PUSCH and UL VoIP is also desirable with a minimum gain of 1 dB forboth medium data rate PUSCH and UL VoIP.

One issue to be resolved is, how to increase efficiency for largebundling 20 dB coverage (e.g., for devices that are plugged into anoutlet). One issue is how to adapt to channel conditions for differentuser conditions where different bundling size is required, instead ofalways using worst case. Another issue to be resolved is what PHICHbundle size to use, for example, if the UE uses PUSCH with bundle size128.

Various approaches to enhance MTC operation with large bundling and lowpower for devices deployed in difficult to reach locations such as abasement are provided herein. Techniques and apparatus are providedherein for enhanced TTI bundling with large bundling size using bundlesize mapping, fixed bundling size, and signaling of bundle size todetermine bundle sizes. Also provided herein are techniques forpersistent scheduling with large bundle size and early termination.

Aspects of the present disclosure provide techniques for enhancedtransmission time interval (TTI) bundling design for machine typecommunications (MTC). TTI bundling size may be fixed by a one-to-one ora one-to-many mapping. Bundling sizes may be determined (or dictated)for a channel based on bundling sizes used for signaled by anotherchannel. Persistent scheduling can also be used to transmit a channel,where a modulation and coding scheme (MCS), rate, or transmit power canbe adjusted for transmission of the channel.

For severely coverage limited UEs, link budget enhancements for all DLchannels may be desired. According to certain aspects, a fixed set ofbundling sizes may be used for all channels. In aspects, there may be aone-to-one mapping without any blind decoding or additional signaling.Alternatively, there may be a one-to-many mapping with limited set ofpossibilities, further down-selected by blind detection or signaling.

According to certain aspects, the combination of bundling sizes for DLand UL channels may be defined in the specification. Alternatively, thebundling sizes for DL and UL channels may be signaled in one-to-one orone-to-many mapping. For example, PBCH may have a fixed bundling size of64, system information block (SIB) may have fixed bundling size of 128,RACH may have a fixed bundling size of 16, and Message 3 may have fixedbundling size of 64. Additionally, PUSCH may have a fixed bundling sizeof 128, PHICH may have a fixed bundling size of 32, and PDCCH may have afixed bundling size of 32. Alternatively, PUSCH may have a fixedbundling size of 16, PHICH may have a fixed bundling size of 4, andPDCCH may have a fixed bundling size of 4. In another alternative, PUSCHmay have a fixed bundling size of 64, PHICH may have a fixed bundlingsize of either 4 or 8, and PDCCH may have a fixed bundling size ofeither 2 or 4.

According to certain aspects, once the UE acquires the system from thefirst channel(s), the UE may know the rest or a limited set ofparameters for other channels. For example, PBCH/SIB/ePDCCH may have afixed mapping of bundle size. In this case, the UE may discover thatPBCH has a bundle size of 8, then the UE may know that SIB has a bundlesize of 16 and ePDCCH has aggregation level 8 and bundle size 8. Inanother example, the UE may discover that PBCH has a bundle size of 16,then the UE may know that SIB has a bundle size of 32 and ePDCCH hasaggregation level 8 and bundle size 16.

In aspects, for RACH, the bundle size of RACH may be signaled inPBCH/SIB or directly mapped to the TTI bundle size of PBCH/SIB. Forexample, based on the bundling size of primary synchronization signal(PSS)/secondary synchronization signal (SSS)/PBCH/SIB, the bundle sizefor RACH Msg 1, 3, 5 may be determined.

According to certain aspects, the bundling size of one channel may bedetermined based on the bundle size of a different channel. In aspects,the UE may determine the bundling size for DL channels based on theassigned bundle size for UL channels. For example, based on the assignedbundle size for PUSCH transmission, the UE may be determine the bundlesize for dynamic PDCCH or PHICH. In aspects, the UE may determine thebundling size for UL channels based on the assigned bundle size for DLchannel. For example, based on the assigned bundling size forePDCCH/PDCCH the UE may determine the bundling size for PUCCH ACK.

Persistent assignments may be used in order to reduce the overhead dueto bundled PDCCH/ePDCCH assignments. However, one drawback of persistentscheduling is that it cannot adapt to channel variation and payload sizechanges. According to certain aspects, large bundling size by may beassigned via persistent scheduling and early termination of a packet maybe allowed. On the UL, the UE may be signaled to transmit with TTIbundle size of N, but provide multiple PHICH resources for the UE tomonitor before it finishes the entire TTI bundle. This may avoid dynamicgrant change and PHICH may have much less overhead and be easier topower boost. Alternatively, the UE may be instructed to monitor dynamicPDCCH grant to indicate both early termination and new transmission. Inaspects, the instruction may be indicated in the specification or viasignaling.

As an example, PUSCH transmission may be persistently scheduled for TTIbundle size of 128, but allow the UE to early terminate at TTI bundle of64 or 96. Thus, if the eNB early decodes, it can signal the UE to stoptransmitting over the remaining TTIs. The PHICH may still map to thephysical resource block (PRB). Additionally, PHICH can be bundled orpower boosted for link budget improvements

According to certain aspects, PS may have fixed RB size. Modulation andcoding scheme (MCS)/rates may be adapted, within a limited set, based onUL payload size or may be linked to power control and early termination.This may provide PDCCH/ePDCCH overhead and power savings. On the UL,this can be UE rate selection or eNB blind decoding of full rate/halfrate, etc.

According to certain aspects, if early termination is supported, thenthe UE may transmit at max power and rely on early termination to adaptto the channel and interference conditions. If early termination is notsupported, the UE may automatically adjust transmit power according tothe chosen transport block (TB) size and keep the same bundled TTItransmission. According to certain aspects, on the DL, the eNB canprovide multiple rates within the persistent assignment (UE may blinddecode) and allow the UE to transmit PHICH for early termination.

FIG. 5 illustrates example operations 500 for wireless communications,in accordance with certain aspects of the present disclosure. Theoperations 500 may be performed, for example, by a wireless device. Theoperations 500 may begin, at 502, by determining a mapping of one ormore uplink (e.g., PUSCH, RACH Msg 1, RACH Msg 3) or downlink (e.g.,PDCCH, PBCH, PHICH, SIB) channels to one or more fixed bundling sizes,wherein each bundling size indicates a number of transmission timeintervals (TTIs) over which a channel should be transmitted. In aspects,the mapping may be a one-to-one mapping of that channel to a singlefixed bundling size or a one-to-many mapping of a channel to a set ofpotential bundling sizes.

At 504, the wireless device processes transmission of the one or moreuplink or downlink channels based on the mapping. For example, thedevice may transmit and/or receive the one or more uplink or downlinkchannels in accordance with the mapping. According to certain aspects,the wireless device may determine an actual bundling size used from theset via blind detection. In aspects, the wireless device may receivesignaling indicating one or more bundling sizes from the set.

In aspects, a bundling size for one channel may dictate a bundling sizefor one or more other channels. For example, the bundling size for eachof the one or more other channels may be proportionate to the bundlingsize number of the one channel. Alternatively, the bundling size for anuplink channel may dictate a bundling size for one or more downlinkchannels or a bundling size for the downlink channel may dictate abundling size for the one or more uplink channels.

In aspects, a bundling size for a RACH may be signaled in a PBCH or aSIB. Alternatively, a bundling size for RACH is mapped to a bundlingsize of a PBCH or a SIB. In aspects, a bundling size of Msg 1 (RACH),Msg 2 (RACH response), Msg 3, or Msg 4 may be mapped to a bundling sizeof at least one of PSS, SSS, PBCH, or SIB. In aspects, the bundling sizeof a RACH message is determined based on the bundling size of adifferent RACH message. For example, the bundling size for RACH Msg 2may be determined based on the bundling size for RACH Msg 1 or RACH Msg3.

FIG. 6 illustrates example operation 600 for wireless communications, inaccordance with certain aspects of the present disclosure. Theoperations 600 may be performed, for example, by a wireless device. Theoperations 600 may begin, at 602, by determining persistent scheduling(PS) assignment for a bundling size specifying a number of transmissiontime intervals (TTIs) to be used for transmissions of at least onechannel.

At 604, the wireless device transmits the at least one channel in one ormore TTIs.

At 606, the wireless device terminates transmission of the at least onechannel prior to reaching the number of TTIs specified by the bundlingsize, in response to receiving an indication (e.g., via a PDCCH grant orPHICH) a receiving device successfully received the at least onechannel.

FIG. 7 illustrates example operations 700 for wireless communications,in accordance with certain aspects of the present disclosure. Theoperations 700 may be performed, for example, by a wireless device. Theoperations 700 may begin, at 702, by receiving an indication ofpersistent scheduling (PS) assignment for a bundling size specifying anumber of transmission time intervals (TTIs) to be used fortransmissions of at least one channel.

At 704, the wireless device receives the at least one channel in one ormore TTIs.

At 706, the wireless device transmits an indication (e.g., via PDCCHgrant, ePDCCH, PHICH, or a bundled version of PDCCH, ePDCCH, or PHICH)to terminate transmission of the at least one channel prior to reachingthe number of TTIs specified by the bundling size, if the at least onechannel is received successfully.

FIG. 8 illustrates example operation 800 for wireless communications, inaccordance with certain aspects of the present disclosure. Theoperations 800 may be performed, for example, by a wireless device. Theoperations 800 may begin, at 802, by determining persistent scheduling(PS) assignment (e.g., indicating a bundle size of TTIs) for a fixednumber of resource blocks (RBs) to transmit at least one channel.

At 804, the wireless device adjusts at least one a modulation and codingscheme (MCS), rate, or transmit power when transmitting the at least onechannel. For example, the wireless device may adjust the MCS, rate, ortransmit power based on payload size of the channel. In aspects, thewireless device may adjust between a limited set of MCS or rates.According to certain aspects, the wireless device may terminatetransmission of the at least one channel prior to reaching the number ofTTIs specified by the bundling size, in response to receiving anindication a receiving device successfully received the at least onechannel. In aspects, the at least one channel is an uplink channel andthe adjusting comprises transmitting the uplink channel at a UE-selectedrate.

FIG. 9 illustrates example operation 900 for wireless communications, inaccordance with certain aspects of the present disclosure. Theoperations 900 may be performed, for example, by a wireless device. Theoperations 900 may begin, at 902, by determining persistent scheduling(PS) assignment (e.g., indicating a bundle size of TTIs) for a fixednumber of resource blocks (RBs) to transmit at least one channel.

At 904, the wireless device processes (e.g., blind detection todetermine an adjusted rate) a transmission of the at least one channel,wherein at least one of a modulation and coding scheme (MCS), rate, ortransmit power may be adjusted when transmitting the at least onechannel. For example, the wireless device may adjust the MCS, rate, ortransmit power based on payload size of the channel. In aspects, thewireless device may adjust between a limited set of MCS or rates. Inaspects, the wireless device may receive signaling indicating a set ofrates available within the PS assignment.

According to certain aspects, the wireless device may terminatetransmission of the at least one channel prior to reaching the number ofTTIs specified by the bundling size, in response to receiving anindication a receiving device successfully received the at least onechannel. In aspects, the at least one channel is an uplink channel andthe adjusting comprises transmitting the uplink channel at a UE-selectedrate.

The term “or” is intended to mean an inclusive “or” rather than anexclusive “or.” That is, unless specified otherwise, or clear from thecontext, the phrase, for example, “X employs A or B” is intended to meanany of the natural inclusive permutations. That is, for example thephrase “X employs A or B” is satisfied by any of the followinginstances: X employs A; X employs B; or X employs both A and B. Inaddition, the articles “a” and “an” as used in this application and theappended claims should generally be construed to mean “one or more”unless specified otherwise or clear from the context to be directed to asingular form. As used herein, a phrase referring to “at least one of” alist of items refers to any combination of those items, including singlemembers. As an example, “at least one of: a, b, or c” is intended tocover: a, b, c, a-b, a-c, b-c, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software/firmwarecomponent(s) and/or module(s), including, but not limited to a circuit,an application specific integrated circuit (ASIC), or processor.Generally, where there are operations illustrated in Figures, thoseoperations may be performed by any suitable corresponding counterpartmeans-plus-function components.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or combinations thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, software/firmware, or combinations thereof. To clearlyillustrate this interchangeability of hardware and software/firmware,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware orsoftware/firmware depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in asoftware/firmware module executed by a processor, or in a combinationthereof A software/firmware module may reside in RAM memory, flashmemory, ROM memory, EPROM memory, EEPROM memory, PCM (phase changememory), registers, hard disk, a removable disk, a CD-ROM, or any otherform of storage medium known in the art. An exemplary storage medium iscoupled to the processor such that the processor can read informationfrom, and write information to, the storage medium. In the alternative,the storage medium may be integral to the processor. The processor andthe storage medium may reside in an ASIC. The ASIC may reside in a userterminal. In the alternative, the processor and the storage medium mayreside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software/firmware, or combinations thereof. Ifimplemented in software/firmware, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software/firmware is transmitted from awebsite, server, or other remote source using a coaxial cable, fiberoptic cable, twisted pair, digital subscriber line (DSL), or wirelesstechnologies such as infrared, radio, and microwave, then the coaxialcable, fiber optic cable, twisted pair, DSL, or wireless technologiessuch as infrared, radio, and microwave are included in the definition ofmedium. Disk and disc, as used herein, includes compact disc (CD), laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein, but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communications by awireless device, comprising: determining a mapping of one or more uplinkor downlink channels to one or more fixed bundling sizes, wherein eachof the one or more fixed bundling sizes indicates a number oftransmission time intervals (TTIs) over which a channel should betransmitted; and processing transmission of the one or more uplink ordownlink channels based on the mapping.
 2. The method of claim 1,wherein a bundling size for a channel dictates a bundling size for oneor more other channels.
 3. The method of claim 2, wherein a bundlingsize for an uplink channel dictates a bundling size for one or moredownlink channels.
 4. The method of claim 2, wherein a bundling size fora downlink channel dictates a bundling size for one or more uplinkchannels.
 5. The method of claim 3, wherein a bundling size for aphysical broadcast channel (PBCH) dictates a bundling size for a systeminformation block (SIB) and an enhanced physical downlink controlchannel (PDCCH).
 6. The method of claim 1, wherein a bundling size for arandom access channel (RACH) is signaled in at least one of a physicalbroadcast channel (PBCH) or a system information block (SIB).
 7. Themethod of claim 1, wherein a bundling size for random access channel(RACH) is mapped to a bundling size of at least one of a physicalbroadcast channel (PBCH) or a system information block (SIB).
 8. Themethod of claim 1, wherein the mapping comprises mapping a bundling sizeof at least one of a Msg 1 (random access channel (RACH)), a Msg 2 (RACHresponse), a Msg 3, or a Msg 4 to a bundling size of at least one ofprimary synchronization signal (PSS), secondary synchronization signal(SSS), physical broadcast channel (PBCH), or system information block(SIB).
 9. The method of claim 8, further comprising a bundling size of afirst RACH message based on a bundling size of a different RACH message.10. The method of claim 1, wherein the one or more uplink or downlinkchannels comprise: at least one of a physical uplink shared channel(PUSCH), a random access channel (RACH) Msg 1, or a RACH Msg
 3. 11. Themethod of claim 1, wherein the one or more uplink or downlink channelscomprise at least one of a physical downlink control channel (PDCCH), aphysical broadcast channel (PBCH), a physical HARQ indicator channel(PHICH), or a system information block (SIB).
 12. The method of claim 1,wherein the processing comprises identifying a bundling size for adownlink channel based on an assigned bundling size for an uplinkchannel.
 13. The method of claim 12, wherein the processing comprisesidentifying a bundling size for at least one of a physical downlinkcontrol channel (PDCCH) or a physical HARQ indicator channel (PHICH)based an assigned bundling size for a physical uplink shared channel(PUSCH).
 14. The method of claim 1, wherein the processing comprisesidentifying a bundling size for an uplink channel based on a bundlingsize for a downlink channel.
 15. The method of claim 14, wherein theprocessing comprises identifying a bundling size for a physical uplinkcontrol channel (PUCCH) acknowledgment (ACK) based on a bundling sizefor an enhanced physical downlink control channel (PDCCH) or PDCCH. 16.The method of claim 1, wherein the processing comprises transmitting theone or more uplink or downlink channels in accordance with the mapping.17. The method of claim 1, wherein the processing comprises receivingthe one or more uplink or downlink channels transmitted in accordancewith the mapping.
 18. The method of claim 1, wherein the mappingcomprises, for at least one channel, a one-to-one mapping of the channelto a single fixed bundling size.
 19. The method of claim 1, wherein themapping comprises, for at least one channel, a one-to-many mapping ofthe channel to a set of potential bundling sizes.
 20. The method ofclaim 19, further comprising determining an actual bundling size usedfrom the set of potential bundling sizes via blind detection.
 21. Themethod of claim 20, further comprising receiving signaling indicatingone or more bundling sizes from the set of potential bundling sizes. 22.An apparatus for wireless communications by a wireless device,comprising: means for determining a mapping of one or more uplink ordownlink channels to one or more fixed bundling sizes, wherein each ofthe one or more fixed bundling sizes indicates a number of transmissiontime intervals (TTIs) over which a channel should be transmitted; andmeans for processing transmission of the one or more uplink or downlinkchannels based on the mapping.
 23. The apparatus of claim 22 wherein abundling size for a channel dictates a bundling size for one or moreother channels.
 24. The apparatus of claim 22, wherein a bundling sizefor a random access channel (RACH) is signaled in at least one of aphysical broadcast channel (PBCH) or a system information block (SIB).25. The apparatus of claim 22, wherein a bundling size for random accesschannel (RACH) is mapped to a bundling size of at least one of aphysical broadcast channel (PBCH) or a system information block (SIB).26. The apparatus of claim 22, wherein the processing comprisesidentifying a bundling size for a downlink channel based on an assignedbundling size for an uplink channel.
 27. The apparatus of claim 22,wherein the mapping comprises, for at least one channel, a one-to-onemapping of the channel to a single fixed bundling size.
 28. Theapparatus of claim 22, wherein the mapping comprises, for at least onechannel, a one-to-many mapping of the channel to a set of potentialbundling sizes.
 29. An apparatus for wireless communications by awireless device, comprising: at least one processor configured to:determine a mapping of one or more uplink or downlink channels to one ormore fixed bundling sizes, wherein each of the one or more fixedbundling sizes indicates a number of transmission time intervals (TTIs)over which a channel should be transmitted; and process transmission ofthe one or more uplink or downlink channels based on the mapping; and amemory coupled with the at least one processor.
 30. A computer programproduct for wireless communications comprising a computer readablemedium having instructions stored thereon, the instructions executableby one or more processors, for: determining a mapping of one or moreuplink or downlink channels to one or more fixed bundling sizes, whereineach of the one or more fixed bundling sizes indicates a number oftransmission time intervals (TTIs) over which a channel should betransmitted; and processing transmission of the one or more uplink ordownlink channels based on the mapping.